1. Field of the Invention
The invention generally relates to free wings for aircraft and more particularly a free wing attached to a fuselage of an aircraft in a manner such that the wing is free to oscillate about a spanwise axis forward of its aerodynamic center as it is subjected to aerodynamic pitching moments imposed by lift and drag forces. The wing is trimmed through a use of a free canard which serves as stabilizer for controlling the angle of attack of the wing.
The so-called "simple free wing" embodies a concept of an unconventional attachment of a wing to a fuselage in a manner such that the wing is free to pivot about its spanwise axis forward of its aerodynamic center, and is subject only to aerodynamic pitching moments imposed by wing lift and drag.
Among the various advantages realized when employing a free wing are alleviation of gust loads, simplicity in fuselage design, extension of travel limits for center of gravity, improved fuselage attitude trim, avoidance of fuselage rotation at lift-off and landings, and increased freedom in design location for landing gear.
2. Description of the Prior Art
Heretofore, numerous attempts have been made to provide for conventional aircraft, particularly in the field of general aviation, a practical free wing, whereby the numerous advantages, some heretofore enumerated, more readily can be realized. Among the approaches heretofore taken are embraced in the teachings of U.S. Pat. No. 2,347,230 to Zuck. Of course, a free wing must be trimmed if it is to serve a practical purpose. Patentee Zuck suggests a use of control surfaces comprising trailing edge flaps for this purpose.
While the patented free wing, generally speaking, may function satisfactorily for its intended purpose, it should readily be appreciated that the free wings of the prior art suffer a common inadequacy in that not only is drag increased as a consequence of negative flap deflection, but the effective surface area of the wing is decreased with an attendant loss in the lift coefficient as lift producing capabilities of the wing. This characteristic of the patented free wing becomes particularly significant when the aircraft is on final approach and/or during takeoff, as can readily be appreciated by those familiar with the handling of aircraft in flight.
It is therefore the purpose of the instant invention to provide a free wing having a capability of achieving pitch trim, without experiencing an attendant loss of lift coefficient whereby the known advantage of the free wing may be realized while the recognized disadvantages which heretofore plagued designers of free wings are avoided.